Looks good to me. Like Crazy said you could shrink port area down if you want. I don't think it would be necessary though, that's already a pretty big box for two 10"s.
It looks like (what I assume is your depth) is 13.5" outer, and your port width will the 3.5". That leaves you with 13.5 - .75 (front wall) - .75 (back wall) - .75 (port wall) - 3.5 (port width) = 7" of depth. That should be fine, but just something to think about clearance wise.